Essentially Epicurus affirms that there is a God, this God is “immortal and happy” ....
...why is God immortal and happy? Why does he never get irritated? Why doesn’t he have any administration? Why doesn’t he interact with humankind?...
Matt, I might be nit-picking but I think there is an important point to make here. Epicurus never referred to "God," always to "the gods."
To my understanding there is never a single instance of one type of entity in the infinite Epicurean universe, so there can't be God, only gods. Missing this detail, even in apophatic theology, opens the door to a more mystical interpretation than what I think Epicurus had in mind.
Even if using the term "God" is force of habit I think it's important to treat it like certain descriptors that are avoided in the racial justice movement. That's probably a bad example: I'm not saying that saying God comes close to a racial slur! But refining one's vocabulary refines one's thinking.